Circuit Board Repair Guide > Basic Circuit Board Repair Procedures > 2.7 Epoxy Mixing and Handling

CTC 2.7 Epoxy Mixing and Handling

This section covers epoxy mixing and handling. The epoxy used in this procedure has multiple uses including solder mask repair, base board repair, circuitry over-coating and delamination repair.

Note
For high strength or high temperature applications two part epoxies will generally have the best properties.

Related Procedure References
CTC	1.0	Foreword - Circuit Board Repair Guide
CTC	2.1	Handling Electronic Assemblies
CTC	2.2.1	How to Clean a Circuit Board
CTC	2.2.2	Cleaning, Aqueous Batch Process
CTC	2.5	Baking and Preheating
IPC 7721	2.7	Epoxy Mixing and Handling
Tools and Materials
Cleaner Color Agents Epoxy Foam Swabs Heat Lamp		Mixing Cups Mixing Sticks Oven Wipes

Epoxy Specifications - No. 115-3302
The Epoxy used at Circuit Technology Center facilities has the following properties.

Packaging	2 gram prepackaged containers
Color	Clear, transparent
Pot life	30 minutes
Cure cycle	24 hours at room temperature or 1 hour @ 165°F (74°C)
Viscosity (after mixing)	1900 cps @ 77°F (25°C)
Operating temperature range	-76°F to 284°F (-60°C to 140°C)
Hardness	88 Shore D
Dielectric strength	410 volts/mil

PC Board Preparation
The area where the epoxy is to be applied should be prepared prior to mixing the epoxy. This preparation may include preheating the affected area to improve absorption of the applied epoxy. The entire circuit board may also be heated in an oven or with a heat lamp.

Caution
Some components may be sensitive to high temperatures.

Procedure - Prepackaged Two Part Epoxy

Prepackaged epoxy, mix resin and hardener

Figure 1: For prepackaged epoxy, remove divider clip and mix resin and hardener inside package.

Figure 2: Apply epoxy as needed. Foam swabs may be used to add texture for soldermask repair.

1.	Remove the clip separating the resin and hardener. Mix by squeezing both halves together with your fingers. Mix for at least one minute to ensure a complete mix of the resin and activator. (See Figure 1).

2.	Cut open one end of the epoxy tube and squeeze the contents into a mixing cup. Mix again with a mixing stick to ensure a thorough mixture of the resin and hardener. Note For bubble free epoxy, remove the clip separating the resin and hardener. Cut open one end of the Epoxy tube and squeeze the contents into a mixing cup. Slowly stir the mixture with the mixing stick. Be sure to stir the mixture for at least 2 minutes to ensure that all the resin and hardener have completely mixed.
3.	If needed, add color agent to the mixed epoxy. Stir slowly to prevent bubbles.

4.	Apply or use as needed. (See Figure 2).

5.	Cure the epoxy for 24 hours at room temperature or 1 hour @ 165°F (74°C)

Evaluation

1.	Visual examination of epoxy for texture and color match.

2.	Testing of epoxy surface for complete cure.

3.	Electrical tests as applicable.